Web development company, Automattic, has recently announced that its advertising network, WordAds, is now available for self-hosted sites.
Similar to Google's AdWords, the network provides advertisement content on WordPress.com sites and the network can be used via Jetpack and the new AdControl plugin. It can be a great way for sites to earn money but minimum levels of traffic are required to ensure the process is mutually beneficial. More information about the requirements can be found in the site's FAQ. Additionally, the user must have both Jetpack and AdControl installed.
In 2013, Automattic paid out approximately $1 to WordAds users. Statistics for 2015 are not yet publicly available but a significant increase is expected, as WordAds 2.0 has sparked new interest.
For more information about the network and how you can use the service to bring revenue to your site, you can visit the WordAds hub.